Panic when running against repo example

[scooter-dangle]

I tried running

RUST_BACKTRACE=1 cargo run -- example_documents/pagination.md

and I got

    Finished dev [unoptimized + debuginfo] target(s) in 3.06s
     Running `target/debug/mdproof example_documents/pagination.md`
thread 'main' panicked at 'attempted to leave type `linked_hash_map::Node<std::string::String, object::Object>` uninitialized, which is invalid', /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/core/src/mem/mod.rs:660:9
stack backtrace:
   0: rust_begin_unwind
             at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/std/src/panicking.rs:515:5
   1: core::panicking::panic_fmt
             at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/core/src/panicking.rs:92:14
   2: core::panicking::panic
             at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/core/src/panicking.rs:50:5
   3: core::mem::uninitialized
             at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/core/src/mem/mod.rs:660:9
   4: linked_hash_map::LinkedHashMap<K,V,S>::insert
             at /home/scott/.cargo/registry/src/github.com-1ecc6299db9ec823/linked-hash-map-0.3.0/src/lib.rs:203:52
   5: lopdf::object::Dictionary::set
             at /home/scott/.cargo/registry/src/github.com-1ecc6299db9ec823/lopdf-0.17.0/src/object.rs:280:3
   6: <lopdf::object::Dictionary as core::iter::traits::collect::FromIterator<(K,lopdf::object::Object)>>::from_iter
             at /home/scott/.cargo/registry/src/github.com-1ecc6299db9ec823/lopdf-0.17.0/src/object.rs:351:4
   7: printpdf::types::plugins::xmp::xmp_metadata::XmpMetadata::into_obj
             at /home/scott/.cargo/registry/src/github.com-1ecc6299db9ec823/printpdf-0.2.10/src/types/plugins/xmp/xmp_metadata.rs:72:30
   8: printpdf::types::pdf_metadata::PdfMetadata::into_obj
             at /home/scott/.cargo/registry/src/github.com-1ecc6299db9ec823/printpdf-0.2.10/src/types/pdf_metadata.rs:66:10
   9: printpdf::types::pdf_document::PdfDocumentReference::save
             at /home/scott/.cargo/registry/src/github.com-1ecc6299db9ec823/printpdf-0.2.10/src/types/pdf_document.rs:267:58
  10: mdproof::main::run
             at ./src/bin/mdproof.rs:67:5
  11: mdproof::main
             at /home/scott/.cargo/registry/src/github.com-1ecc6299db9ec823/quicli-0.3.1/src/main_macro.rs:45:29
  12: core::ops::function::FnOnce::call_once
             at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/core/src/ops/function.rs:227:5
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.